Computer Networking: Network Layer Control Plane

Vocabulary practice flashcards covering traditional routing algorithms (link-state, distance vector), intra-AS routing (OSPF), inter-AS routing (BGP), Software-Defined Networking (SDN) architectures, and ICMP diagnostics based on Kurose & Ross Chapter 5.

Forwarding (Data Plane)

The network-layer function responsible for transferring arriving packets from a router's input link interface to the appropriate router output link interface.

Routing (Control Plane)

The network-layer function that determines the end-to-end path or route taken by packets as they traverse from a source host to a destination host.

Per-Router Control Plane

The traditional control plane structure where individual routing algorithm components operate on each and every router, interacting with one another to determine forwarding tables.

Software-Defined Networking (SDN) Control Plane

A control plane structure where a logically centralized remote controller computes and installs forwarding tables directly into the data-plane switches.

Link-State (LS) Routing Algorithm

A centralized routing algorithm in which every router possesses complete network topology and link cost information, obtained via link-state broadcast, before computing least-cost paths.

Distance Vector (DV) Routing Algorithm

A decentralized, iterative routing algorithm where routers initially know only direct costs to attached neighbors and iteratively exchange distance vector estimates with neighbors until values converge.

Dijkstra's Algorithm

An iterative link-state algorithm that computes the least-cost path from a single source node to all other destinations in a network, possessing an algorithmic complexity of $O(n^2)$ (or $O(n \log(n))$ with efficient implementations).

Bellman-Ford Equation

The dynamic programming equation used in distance vector routing: $D_x(y) = \min_v \{ c_{x,v} + D_v(y) \}$, which states that the least-cost path from node $x$ to node $y$ is the minimum sum of direct cost $c_{x,v}$ to neighbor $v$ plus $v$'s cost to $y$.

Count-to-Infinity Problem

A routing loop phenomenon in distance vector routing where 'bad news travels slow,' causing neighboring nodes to slowly increment path costs to an unreachable or high-cost destination one step at a time.

Autonomous System (AS)

A region of routers aggregated under a single administrative authority (also called a domain) that typically shares a common intra-domain routing protocol.

Gateway Router

A router situated at the edge of an Autonomous System (AS) that connects directly to one or more routers in other ASes and executes inter-domain routing protocols.

Open Shortest Path First (OSPF)

A publicly available, classic link-state intra-AS routing protocol that floods authenticated link-state advertisements directly over IP and uses Dijkstra's algorithm to compute local forwarding tables.

Area Border Router (ABR)

A router in a hierarchical OSPF deployment that summarizes distances to destinations within its own local area and advertises them into the backbone area.

Border Gateway Protocol (BGP)

The de facto standard inter-domain routing protocol of the Internet that allows autonomous systems to exchange reachability information and implement policy-based routing across domains.

External BGP (eBGP)

A BGP session and protocol mechanism used by gateway routers to obtain and advertise destination subnet reachability information to and from neighboring Autonomous Systems.

Internal BGP (iBGP)

A BGP session and protocol mechanism used to distribute reachability information learned from outside an Autonomous System to all internal routers within that AS.

AS-PATH

A key BGP route attribute that records the list of Autonomous Systems through which a prefix advertisement has passed, used to detect loops and determine route preference.

NEXT-HOP

A BGP route attribute that specifies the IP address of the internal-AS router or interface that begins the path toward the next-hop Autonomous System.

Hot Potato Routing

An inter-domain routing practice where a router forwards a datagram toward the egress gateway router that offers the least intra-domain cost, completely disregarding the inter-domain cost outside the AS.

Northbound API

The interface layer through which an SDN controller exposes network state abstractions and network services to programmable network-control applications.

Southbound API

The protocol and interface layer (such as OpenFlow) that allows an SDN controller to configure, monitor, and push flow tables to data-plane switches.

OpenFlow Protocol

A standardized protocol operating over TCP between an SDN controller and managed switches, providing messages to query features, configure ports, install flow entries, and handle packets.

Internet Control Message Protocol (ICMP)

A network-layer protocol carried directly inside IP datagrams, utilized by hosts and routers for network-level error reporting (e.g., unreachable destinations) and diagnostics (e.g., ping).

Traceroute

A network diagnostic program that sends sets of UDP segments with incrementing Time-To-Live (TTL) values, utilizing ICMP Type 11 Code 0 (TTL expired) and Type 3 Code 3 (port unreachable) messages to trace the path to a destination.